Medium Access Control Protocols For Application-oriented Underwater Acousitc Sensor Networks

Underwater acoustic sensor networks(UWASNs)has great application prospect in ocean observation.Networking technology is the key to UWASN,and medium access control(MAC)technology is the core of networking technology.UWASN has many specific characteristics,such as long propagation delay,high bit error rate,and so on.Meanwhile,UWASN is oriented to application,and different applications have corresponding requirements.Therefore,combining with the network characteristics and specific application requirements,it is of great significance to design MAC protocols for application-oriented UWASNs.Considering the non-uniform distribution of traffic load in the UWASN for data collection,a data-collection-oriented MAC(DCO-MAC)protocol is proposed.In DCO-MAC protocol,the network is partiationed into several sub-networks,and a contention-based MAC(CT-MAC)protocol is performed in sub-networks with light traffic load.In CT-MAC protocol,after receiving the control packets for channel competition from the node having data packets to send,the receiver invites nodes in the same sub-network having data to send to join in the transmission.With one channel competition,the receiver is able to receive the data packets from sevral nodes,achieving a higher throughput.In the sub-networks with heavy traffic load,a reservation-based MAC(RSV-MAC)protocol is carried out.In RSV-MAC protocol,the receiver schedules the transmission of senders,in order to reduce the collision probability of transmission.Meanwhile,the mobile noeds have the priority to access the network first,if there are mobile nodes existing in the network.Theoretical analysis and simulation results show that DCO-MAC protocol achieves a higher network throughput,lower end-to-end delay and energy consumption,and better fairness performance of sensor nodes.Underwater target detection using the UWASN is a hot research topic.According to the real-time requirements of underwater target detection,an underwater target dection MAC(UTD-MAC)protocol is proposed.In the proposed UTD-MAC protocol,nodes detecting target send data packets containing the target state information to the fusion center.In order to avoid the collision of transmission and achieve a low end-to-end delay of data packets,the transmission of data packets is scheduled by the fusion center.In the process of forwarding the packet containing the target state information from the fusion center to sink node,a parallel handshaking method is adopted.That is,a node reserves the channel with the node in next hop when waiting for the data packets from the node in last hop.Therefore,data packets can be transmitted to the node in next hop immediately after receiving data packets from node in last hop,which results in a lower end-to-end delay of data packets.Theoretical analysis and simulation results show that the proposed UTD-MAC protocol can reduce the energy consumption and end-to-end delay of data packets,and improve the target tracking accuracy.The experimental verification of the proposed UTD-MAC protocol is carried out.Experimental results are consistent with theoretical results.It shows that the UTD-MAC protocol can reduce the end-to-end delay of data packets.